The cloning and expression of the recombinant osteogenic proteins of the BMP-2 family has previously been described (J.M. Wozny, et al., Science 242:1528-1534 (1988); E.A. Wang, et al., Proc. Natl. Acad. Sci. USA 87:2220-2224 (1990), incorporated herein by reference). Osteogenic proteins of the BMP-2 family are a promising development in the bone and cartilage field. The BMP-2 family of proteins includes BMP-3, BMP-4, BMP-5, BMP-6 and BMP-7, and bone-inducing proteins and proteins which are encoded by DNA sequences which hybridize thereto under stringent conditions. The DNA sequence of BMP-2 is shown in SEQ ID No:1.
These osteogenic proteins may be produced in cultured mammalian cell lines by transformation with an expression vector containing the respective cDNAs. The yield of expressed recombinant bone-inducing proteins can be increased in accordance with the present invention by addition of dextran sulfate to the cell culture medium.